Roy Keane has aimed another barb at former Manchester United boss Sir Alex Ferguson by claiming he wasn't the best manager he ever worked with.
The pair's tumultuous relationship was thrust into the limelight once more recently following claims made by Ferguson in his autobiography, which was released in October following his retirement from the game.
In My Autobiography Ferguson hit out at Keane for giving an interview to Manchester United's official television station back in 2005 in which he criticised a number of his team-mates - an incident which ultimately led to the midfielder's departure from Old Trafford.
Keane hit back soon after the book was published, describing Ferguson's version of events as 'lies' and also questioning the Manchester United boss of 26 years' loyalty.
Speaking ahead of the broadcast of ITV documentary Best of Enemies - which focuses on Keane's rivalry with former Arsenal midfielder Patrick Vieira - the ex-Manchester United captain says Ferguson, who won an incredible 13 Premier League trophies and two Champions Leagues during his time at Old Trafford, isn't the best he worked with.
When asked who was the best he'd worked under, Keane replied: "Brian Clough".
When pushed to elaborate, the Republic of Ireland assistant manager simply added: "You asked me the question, I answered it."
The 42-year-old also defended his comments made during the interview with MUTV, claiming many of them were "tongue in cheek".
Keane worked with Clough, a double European Cup winner during his time with Nottingham Forest, before leaving the City Ground to join Manchester United in 1993.
Despite the timing of his comments, Keane has previously insisted Clough was the best manager he has ever worked under, describing him as an 'absolute genius' back in 2008.
Keane & Vieira - Best of Enemies will be screened on ITV4 in the UK at 10.30pm tomorrow evening.